Cutaneous manifestations of inflammatory bowel disease

Extraintestinal manifestations are common in inflammatory bowel disease, and skin lesions are among the most described extraintestinal findings. Reports indicate an incidence of cutaneous manifestations ranging from 2 to 34%.1 The true incidence of cutaneous disease may be significantly higher as lesions such as pyoderma gangrenosum or metastatic Crohn’s disease are difficult to diagnose and are therefore overlooked. In the current issue of the JEADV, Yosipovitch et al. present a new manifestation of Crohn’s disease, neutrophilic lobular panniculitis with non-caseating granulomas (pp. 405–406). The cutaneous manifestations of inflammatory bowel disease may be specific lesions such as oral Crohn’s disease and metastatic Crohn’s disease where there is direct involvement of mucous membranes or skin by the same disease process. Alternatively, many patients develop reactive skin disease such as erythema nodosum, pyoderma gangrenosum, and pustular eruptions which are non-specific reaction patterns. Finally, miscellaneous cutaneous manifestations such as psoriasis and clubbing are more prevalent in patients with inflammatory bowel disease. This editorial will review some of the noteworthy skin disorders associated with inflammatory bowel disease. Pyoderma gangrenosum, one of the most therapeutically and diagnostically challenging skin diseases, is associated with both ulcerative colitis and Crohn’s disease. Ulcerative and pustular variants of pyoderma gangrenosum have been described. Pyoderma gangrenosum can be difficult to distinguish from other more common ulcerating lesions. There are a number of features that help distinguish pyoderma gangrenosum from other causes of cutaneous ulceration. Lesions often begin as pustules that rapidly ulcerate and form crater-like holes overlying pus-filled fistulous tracts. Pyoderma gangrenosum almost always involves the legs or peristomal sites, although it can develop anywhere on the body’s surface including the face. The association with inflammatory bowel disease is one of the features that helps distinguish pyoderma gangrenosum from other malignant, infectious and vascular aetiologies. It has been reported that approximately 5% of patients with ulcerative colitis will develop pyoderma gangrenosum, with a slightly lower prevalence in patients with Crohn’s disease.2 Pathergy, the development of ulcerations following trauma, is fairly specific for pyoderma gangrenosum. The only other condition associated with pathergy is Behcet’s disease. Therapy depends on the extent of the involvement and is aimed at treating both the generalized inflammatory bowel disease and the lesions of pyoderma gangrenosum. Localized lesions may only require intralesional injection of corticosteroids such as triamcinolone acetonide. More extensive disease may require large daily doses of prednisone or other immunosuppressive agents such as cyclosporin or FK 506. More recently, there is growing evidence to suggest that thalidomide may be beneficial in treating recalcitrant pyoderma gangrenosum. Rapid and dramatic results have been seen in patients treated with cyclosporin. Other novel therapies include topical tacrolimus (FK 506) and mycophenolate mofetil. Pustular eruptions have been described in some patients with ulcerative colitis. They are described as grouped erythematous vesiculo-pustules that eventually crust and heal with postinflammatory hyperpigmentary alteration3 Some of the pustular eruptions develop into necrotic plaques or ulcers, and therefore resemble the lesions of pyoderma gangrenosum. Thus, there is a debate as to whether these lesions are actually an entity unto themselves or if they represent an inflammatory response incapable of inducing the necrosis, thus forming the ulcer that is representative of pyoderma gangrenosum. Erythema nodosum, another common cutaneous manifestation of inflammatory bowel disease, consists of tender red nodules that occur primarily on the anterior portion of the lower extremities. Histopathologically, the nodules represent a septal panniculitis. Erythema nodosum has been reported to have an incidence of 2–4% in patients with inflammatory bowel disease and up to 20% of patients in an active phase of disease.4,5 Although the underlying pathogenesis is unknown, erythema nodosum is thought to be a hypersensitivity response to a number of inciting agents. As opposed to pyoderma gangrenosum, whose lesions ulcerate, erythema nodosum does not ulcerate and, as a result, heals without scarring or atrophy. Therefore, treatment consists of controlling the underlying flare of bowel disease by administration of oral non-steroidal anti-inflammatory medications, intralesional injection of corticosteroids, oral potassium iodide, dapsone, and colchicine. Metastatic Crohn’s disease is characterized by cutaneous granuloma formation distant from the gastrointestinal tract in patients with Crohn’s disease. It is a specific lesion representing a non-caseating granulomatous histology identical to the underlying disease. Of note, the term metastatic is a misnomer; it is not contagious or capable of distant metastasis in the ways demonstrated by other pathologies that we connote ‘malignant.’ The clinical appearance of metastatic Crohn’s disease is variable. For example, lesions in the intertriginous areas present as ulcerations while lesions on the arms and legs generally present as tender nodules or lichenoid papules. However, when the lesions appear on the legs they may parallel the characteristics of erythema nodosum, making diagnosis difficult. Therapy for the most part consists of treating the underlying inflammatory bowel disorder, which for some has resulted in resolution of the skin lesions. Other treatments consist of topical therapies but have demonstrated limited remission5 In this issue of the JEADV, Yosipovitch et al. present a patient with Crohn’s disease and erythema nodosum-like lesions, which on biopsy demonstrate a neutrophilic globular panniculitis with non-caseating granulomas. The skin lesions resolved spontaneously 6 weeks after they developed. There have been a few reports that have suggested an increased association between inflammatory bowel disease and psoriasis. One study indicated a prevalence of psoriasis in 9.6% in patients with Crohn’s disease compared to 2.2% of the controls6 Other cutaneous manifestations are related to hypercoagulability, or to treatments used for inflammatory bowel disease. While some of the skin lesions associated with inflammatory bowel disease are distinctive and easily diagnosed, the spectrum of cutaneous manifestations is broad and varied. When the aetiologies of ulcerative colitis and Crohn’s disease are better understood, we will undoubtedly have a better understanding of why particular cutaneous lesions occur in inflammatory bowel disease.